Build problem on ABM AIX + solution

[Brian Gough]

gsl-discuss@lists.thewrittenword.com writes:
 > > Let me know and I'll make the change.
 > 
 > Ick. This is not necessary. We have *no* problems with GSL 0.9.2 on
 > AIX 4.3.2 with xlc 5.0.2.0.
 > 

This change is recommended in the autoconf manual so I plan to apply
it anyway, but I'd like to know if it fixes this problem (it should do
I think).

 - Macro: AC_HEADER_STDC
     Define `STDC_HEADERS' if the system has ANSI C header files.
     ....

     Use `STDC_HEADERS' instead of `__STDC__' to determine whether the
     system has ANSI-compliant header files (and probably C library
     functions) because many systems that have GCC do not have ANSI C
     header files.